Inverters are used in photovoltaic (PV) systems to convert power provided by solar modules as direct current to alternating current in order to be able to feed said power into a grid. The power generated jointly by a multiplicity of solar modules is typically converted to AC voltage by way of an inverter, wherein transformerless inverters permit particularly efficient conversion. In particular, transformerless inverters that feed in a single-phase manner and have a full-bridge topology generally do not permit grounding of the solar modules during operation because the potential reference with respect to ground potential changes with the grid frequency. Said grid-frequency potential change, in connection with construction-dictated stray capacitances at the solar modules, leads to stray currents, the amplitude of which can assume increased values, for example in the case of rain. PV systems have differential current sensors for reasons of operational safety. Since the stray current is superposed with the fault current of the system and contributes to a fault current value measured by the differential current sensors, an increased stray current can lead to premature tripping of protection mechanisms based on fault current measurements, as a result of which the PV system automatically switches off, even though safe operation would still be possible.